Dyslexia involves difficulties in reading and writing in individuals with normal or above normal intelligence. It is a serious handicap affecting about 5-8% of the population, and frequently results in social and economic problems. Dyslexia has a neurological background with a strong hereditary basis. Whether the hereditary form of dyslexia is caused by a major gene or whether it is the additive effect of a number of genes is not known. Our long-term objective is to determine any genetic factors involved in dyslexia which will assist in early diagnosis and support and treatment leading to relatively normal development of reading and writing skills of affected individuals. A collaboration has been initiated with investigators in Sweden to study the genetics of dyslexia. Sweden has a relative homogenous population with a unique church-record system. Families often stay at the same location for several generations, making Sweden a suitable place for this study. A current Swedish research project, "Reading Development in Kronoberg", provides an excellent basis for collaboration. Initially, we plan to study 15-20 families. We will receive pedigrees and decide from which family members blood samples shall be taken. Efforts will be made avoid including study subjects with an attention deficit or/and hyperactivity disorder. To date we have received blood samples from 3 families and immortal cell lines have been established. Linkage studies on extracted DNA will be carried out using conventional parametric and non-parametric linkage methods. Eventually, positional cloning procedures will be used to clone candidate genes for dyslexia. A collaborative effort with American teams is being established.